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mb_2069 [2017/09/18 20:21] antichambre [Specifications] |
mb_2069 [2017/11/08 10:33] antichambre [Choices made during prototyping] |
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==== Precious information found about the 2069 once prototyped ==== | ==== Precious information found about the 2069 once prototyped ==== | ||
- | <WRAP center round info 60%> | + | <wrap info>The Absolute Rating Voltage is +/-5V, tried and fried ;)</wrap>\\ |
- | The Absolute Rating Voltage is +/-5V, tried and fried ;)\\ | + | <wrap info>CV inputs are in a 0 to 5V range.</wrap>\\ |
- | </WRAP> | + | <wrap info>All audio inputs are bipolar and support OverVoltage. A good hard clipping.</wrap>\\ |
- | <WRAP center round info 60%> | + | <wrap info>The SIG1 and SIG2 has inverted signal audio inputs.</wrap>\\ |
- | CV inputs are in a 0 to 5V range.\\ | + | |
- | </WRAP> | + | |
- | <WRAP center round info 60%> | + | |
- | All audio inputs are bipolar and support OverVoltage. A good hard clipping.\\ | + | |
- | </WRAP> | + | |
- | <WRAP center round info 60%> | + | |
- | The SIG1 and SIG2 has inverted signal audio inputs. | + | |
- | </WRAP> | + | |
<WRAP clear></WRAP> | <WRAP clear></WRAP> | ||
It seems all VCA cells invert the signal, then same thing for the VCA part.\\ | It seems all VCA cells invert the signal, then same thing for the VCA part.\\ | ||
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</WRAP> | </WRAP> | ||
</WRAP> | </WRAP> | ||
- | <WRAP center round info 60%> | + | <wrap info>LOG CV Input for cut-off Frequency is inverted input.</wrap>\\ |
- | LOG CV Input for cut-off Frequency is inverted input.\\ | + | |
- | </WRAP> | + | |
Lowest frequency is at 5V, Highest at 0V.\\ | Lowest frequency is at 5V, Highest at 0V.\\ | ||
This CV needs to be inverted too.\\ | This CV needs to be inverted too.\\ | ||
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- | <WRAP center round info 60%> | + | <wrap info>LOG CV Input of the VCA seems unusable.</wrap>\\ |
- | LOG CV Input of the VCA seems unusable.\\ | + | |
- | </WRAP> | + | |
I've got only some NJM2069**BD** for spare then I used the **D** version present in my EX-800 to test Log CV of the VCA in the 2 versions, and it appears to be definitively not usable for both!\\ | I've got only some NJM2069**BD** for spare then I used the **D** version present in my EX-800 to test Log CV of the VCA in the 2 versions, and it appears to be definitively not usable for both!\\ | ||
Maybe some other version (AD, DA...) of the chip release this function. I don't know.\\ | Maybe some other version (AD, DA...) of the chip release this function. I don't know.\\ | ||
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</WRAP> | </WRAP> | ||
+ | <WRAP group> | ||
+ | <WRAP half column> | ||
+ | {{ :antichambre:par_config.jpg?320 |}} | ||
+ | Mode 1 - <wrap hi>PAR</wrap>, VCA Parallel VCF\\ | ||
+ | They share same Input and Output. | ||
+ | </WRAP> | ||
+ | <WRAP half column> | ||
+ | {{:antichambre:sum_mode.jpg?320|}}\\ | ||
+ | Mode 2 - <wrap hi>SUM</wrap>, VCA + VCF, \\ | ||
+ | They share only output.\\ | ||
+ | VCF direct input is tied to ground. | ||
+ | </WRAP> | ||
+ | </WRAP> | ||
+ | \\ | ||
+ | For this purpose I use 3x DG413 Analog Switch on the breadboard.\\ | ||
+ | I reduced it to 1x DG333 and 1x DG413 on PCB.\\ | ||
+ | All Audio purpose active components like OpAmps and Analog Switches are connected to +/-12V. We wants 2069 distortion only!\\ | ||
+ | The 2069 is supplied by +/-5V, then it will be the first to saturate.\\ | ||
+ | \\ | ||
+ | This is the block diagram of the switching circuit | ||
+ | {{ :antichambre:block_mode.jpg |}}\\ | ||
+ | Here the circuit is in default state.\\ | ||
+ | The 2P/4P switch has its own line control.\\ | ||
+ | The two Bypass SPST form a SPDT Switch and have their own control line too.\\ | ||
+ | All others 5 switches are for Mode purpose.\\ | ||
+ | 5 is too much lines, remember I've got only 4 modes then I may reduce it to 2bits, 2 coding lines.\\ | ||
+ | I inserted the Switches in the circuit to get this truth table:\\ | ||
+ | {{ :antichambre:truthtable.jpg?200 |}}\\ | ||
+ | As you can see E=B and D=C then it's reduced to 3 lines.\\ | ||
+ | Now I add my 2 required inputs lines, ModeA and ModeB\\ | ||
+ | We can extract that:\\ | ||
+ | {{ :antichambre:truthtable_reduced2.jpg?400 |}} | ||
+ | It's ok, I need 1x OR gate and 1x AND gate, on PCB I use 2 small 74HC1G32 and 74HC1G08. | ||
+ | And finally I obtain to <wrap hi>control everything with 4 lines</wrap>:\\ | ||
+ | * 1 logic line for Bypassing, Active at High. | ||
+ | * 1 logic line for 2P/4P switching, 4P at Low, 2P at High. | ||
+ | * 2 logic lines to code the 4 Configuration Modes. | ||
+ | <wrap tip>Obviously you're not obliged to use this switching circuit. All I/O are individually accessible on pin header.\\ | ||
+ | You can use it to access I/O or to set it in the static configuration of your choice. | ||
+ | </wrap> | ||
+ | - About the CV inputs of the chip: | ||
+ | I chose to use some 0 to 5V RRIO OpAmp, for precision, voltage limiting and as DAC and CV Summing(Inverter) function. | ||